1. Field of the Invention
This invention relates to low D.E. starch hydrolysate syrups which remain clear over a relatively long period of time at high solids concentrations. The syrups are particularly useful as extenders for synthetic sweeteners. The invention is also concerned with a method of preparing said syrups wherein the first step includes increasing the degree of branching of the starch prior to an enzymatic hydrolysis step.
2. Description Of The Prior Art
There are many processes known in the art for producing low D.E. starch hydrolysates. These processes include liquefying an aqueous slurry of starch with an acid, followed by enzymatic conversion, sometimes referred to as saccharification, or liquefying an aqueous slurry of starch with a liquefying enzyme, followed by enzymatic conversion. For example, Dutch Pat. No. 66/12486, published Apr. 3, 1967, discloses a method for hydrolyzing an aqueous slurry of starch with an acid to a D.E. of at least about 7 to no more than about 16, followed by enzymatic conversion with bacterial alpha-amylase to a D.E. in the range of from about 23 to about 35. Belgian Pat. No. 708,104, published June 18, 1968, discloses a method for hydrolyzing an aqueous slurry of starch with an acid or an enzyme to obtain a liquefied starch hydrolysate having a D.E. of less than about 15, followed by enzymatic conversion of the liquefied starch hydrolysate to a D.E. of less than about 25. It is further disclosed in said Belgian patent that exceptional results are obtained by the enzymatic liquefaction of an aqueous slurry of a waxy starch, followed by the enzymatic conversion of the liquefied waxy starch with bacterial alpha-amylase to obtain a starch hydrolysate having a D.E. in the range of from about 5 to about 25. Products produced by this latter method are extremely soluble in water and their syrups are haze resistant at low temperatures for at least three days. These products are commercially available under the trade name "Mor-Rex", sold by CPC International Inc. German Pat. No. 1,955,392, published June 16, 1971, also discloses a process for hydrolyzing an aqueous slurry of starch with an acid or an enzyme to obtain a liquefied starch hydrolysate having a D.E. of not substantially above 3, followed by enzymatic conversion with bacterial alpha-amylase to obtain a starch hydrolysate having a D.E. not substantially above 18.
The aforementioned prior art methods provide a low D.E. product which performs well in many applications, particularly when used as a carrier for synthetic sweeteners. Other applications for the low D.E. starch hydrolysates include use as a bulking or dispersing agent in synthetic creams or coffee whiteners, as a moisture-holding agent in breads, pastries, meats and as a bodying and smoothing agent in puddings, soups and frozen ice desserts.
The low D.E. starch hydrolysates of the aforementioned prior art methods are first prepared in syrup form and generally dried to a solid. However, many users of low D.E. starch hydrolysates desire a liquid product to reduce handling costs and to eliminate the need for redispersing a dried product. It has been found that one cannot store and/or ship starch hydrolysates of the desired low D.E. in highly concentrated form. To date, there is no known economical method for preparing a low D.E. syrup at high solids which is resistant to the formation of haze on storage. The low D.E. starch hydrolysates prepared by the aforementioned prior art methods tend to haze when their syrups are in concentrated form due to the association of the partially degraded starch molecules in the solution. For example, hydrolysates from corn starch having a D.E. less than about 20 when concentrated up to about 70% solids tend to quickly haze upon storage, until the point where the product sets up to a solid. Attempts to produce a low D.E. waxy starch hydrolysate product at about a 70% solids content or above and having a D.E. less than about 15 results in hazing when the syrup is stored for long periods of time, i.e., more than about three days.
Prior art methods for preparing low D.E. starch hydrolysates using the enzyme bacterial alpha-amylase generally have required an additional liquefaction step with either an acid or an enzyme to provide an aqueous dispersion substantially free of residual starch granules. This technique has been considered necessary in order to provide a uniform conversion of the aqueous starch dispersion with the hydrolyzing enzyme. Heretofore, it has been believed that this aqueous liquefaction step has been necessary to prevent the occurrance of very large starch molecules in the low D.E. starch hydrolysate product. The presence of these large starch molecules is objectionable from the standpoint of filtration and retrogradation, the latter of which is associated with haze formation in the low D.E. syrups.
Heretofore, it has been believed that dextrins would not be a suitable starting material for preparing low D.E. starch hydrolysates by conversion of the same with bacterial alpha-amylase. The reason for this belief is because the conditions used in the art to manufacture dextrins result in a bond rearrangement which causes branching to occur, and because of this bond rearrangement, the dextrins are not expected to undergo a significant conversion in order to obtain a starch hydrolysate which will be readily soluble in water.